EFSEC received an application for site certification (ASC) for the Wild Horse Wind Power project on March 9, 2004. The Council voted to approve the project on May 25, 2005, and submitted the recommendation to Governor Christine O. Gregoire on June 8, 2005. Governor Gregoire approved site certification agreement (SCA) on July 26, 2005.
An amendment in October 2005 transferred the SCA from the Wind Ridge Power Partners, LLC, to Puget Sound Energy (PSE). Construction began in October 2005 and was completed in December 2006. In March 2007, PSE requested authorization to add a 500 kilowatt (KW) solar demonstration facility on the Wild Horse site. EFSEC approved the request in April 2007. Construction was started in 2007 and completed in 2008. In July 2008, PSE requested authorization to add 26 new turbines with generating capacity of up to 54 megawatts (MW) on an additional 1,280 acres. PSE later reduced its request to 22 new turbines with an added generating capacity of 44 MW on 960 acres. The request was granted in 2009, and construction was completed the same year.